The air strike hit the bus at the entrance of the city in the mountainous region southwest of Tripoli, Xinhua cited the TV report quoting military sources as saying.
During the past several weeks, NATO forces have intensified strikes against Tripoli and the neighbouring areas.
The city has been the focus of fights between the forces of embattled Libyan leader Muammar Gaddafi and the rebels against his 42-year rule.
NATO took over full command and control of military operations against Libya from the US March 31, following the UN Security Council resolution, which called for imposing a no-fly zone over Libya and authorised "all necessary measures" to protect civilians in Libya.